Recently, the importance of functional safety is increasing. In particular, because automobile-related instruments require to ensure high safety, various regulations are provided for a failure rate, a failure detection rate, and the like, and there is demanded a high failure detection rate with which information on abnormality can be reported immediately when an input signal or a related instrument has any abnormality. On the other hand, when a configuration for failure detection is installed on a large scale, power consumption increases. For this reason, there is desired a signal monitoring circuit that can detect various abnormalities in a simple configuration.